A139115 a(n) = p*(p - 1), where p is A000043(n).

2, 6, 20, 42, 156, 272, 342, 930, 3660, 7832, 11342, 16002, 270920, 367842, 1634562, 4851006, 5200680, 10345872, 18083756, 19558506, 93867032, 98813540, 125720156, 397464032, 470911700, 538634472, 1979938512, 7437768806, 12210802506

Offset: 1

Author

Omar E. Pol, May 10 2008

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..48 (terms 1..47 from Harvey P. Dale)

Crossrefs

Cf. A000043, A036689, A139306, A139307, A139116, A139223, A139224, A139225, A139226.

Programs

Mathematica

#(#-1)&/@MersennePrimeExponent[Range[30]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 15 2020 *)

Formula

a(n) = A000043(n)*(A000043(n) - 1).

Extensions

More terms from Vincenzo Librandi, May 11 2010